The treatment apparatus, using high-voltage plasma in the atmospheric pressure, has been recently proposed for executing an oxidation treatment of NO included in the exhaust gas from e.g., a diesel engine.
When a voltage conversion transformer, often used under a condition of a low frequency band equal to or less than 10 MHz, is used for generating high-voltage plasma, a coiled coil is required to be small in the size and the number of turn thereof. This is because inductance (reactance) should be small at a high frequency wave of 100 MHz or greater. Also, the coil, used as an electric cable, is accordingly required to have small diameter. Consequently, a drawback occurred that large power cannot be supplied. On the other hand, when voltage is set to be large while characteristic impedence is kept to be low (e.g., 50Ω) without executing the aforementioned voltage conversion, power of 10 kW is required for voltage of 1000V (10002·50/2=10 kW), for instance. However, it is actually difficult to provide a power source for supplying the electrical power of the level.
On the other hand, the “Complete NOx Removal Technology Using Nonequilibrium Plasma and Chemical Process (Performances of Ordinary and Barrier Type Plasma Reactors)”, 2000, pp. 243-248, Nihon Kikai Gakkai Ronbunshu 66-646B, The Japan Society of Mechanical Engineers, Japan proposes a parallel-plates type of high-voltage plasma generating apparatus. The parallel-plates type of the high-voltage plasma generating apparatus is configured to generate plasma in an area between electrodes by applying a high-voltage pulse to the electrodes with the use of an electric oscillator for executing oxidation of NO included in the exhaust gas from e.g., an engine. In this case, the frequency of the high-voltage pulse is several kHz, and the peak voltage thereof is 5000-10000V.